Glow plug



March 7, 1939. H. RABEZZANA GLOW PLUG Filed Nov. 14, 1935 /v/ @i w Patented Mar. 7, 1939 UNITED STATES GLOW PLUG Hector Rabeuana, Flint, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 14, 1935, Serial No. 49.845

11 Claims.

My invention relates to glow plugs wherein a wire of high resistance is heated to incandescence by a current of electricity of low voltage, the heated wire being located within the cylinder of an internal combustion engine and the purpose theerof being to ignite the combustible mixture therein. Such plugs are used principally in Diesel engines to ignite the combustible mixture when the engine is being started and are commonly l0 rendered inactive by breaking the circuit in which they are included after the engine is in operation: as in such engines the ignition of the fuel supplied to the working cylinder is due to the high temperature of air compressed therein, after the engine has become heated and during the subsequent operation thereof.

The principal object of my invention is to provide improved insulation for the metallic conductor or conductors through which current is supplied to the member of the plug which is heated to incandescence, as aforesaid, the insulating material being in the form of a granular powder which is packed about the conductor or conductors and the same being materially cheaper, and easier to apply, than the mica or ceramic insulators heretofore commonly used for insulating purposes in glow plugs.

A further object of my invention is to provide a glow plug wherein the high resistance igniting so member or part, which has to be of an alloy adapted to 4resist the action of burning gases upon it and is quite expensive, isreduced in length as compared with the length of such element heretofore commonly used in glow plugs; the said 35 igniting member being welded to short wire sections of good conducting material which in turn are welded to the insulated conductor or conductors enclosed within the shell or casing of the plug..

o A further object of my invention is to provide Figure 2 is a sectional view similar to Figure l but showing a glow plug wherein a single current supply conductor is insulated from the outer shell or casing of the plug.

Figure 3 is a similar sectional view showing the incandescent element of the plug as welded to short sections of wire which in turn are welded to insulated current supply conductors similar to those present in the form oi my invention shown in Figure 1. l0

Referring now to the drawing, and first to Figure l, the numeral 5 designates the outer metallic shell or casing of the plug, the same being hollow, and being exteriorly threaded so as to screw into a threaded opening in the head or cylinder wall l5 of the engine with which the plug is used; to which end it is provided with a hexagonal portion between its ends as shown.

Within the shell 5 are two current supply conductors 6, 'I in the form of rods extending lon- 20 gitudinally of the plug, and having each a longitudinally extending passage; the rods being made of copper or equivalent good conducting material. The inner ends of these rods are provided with enlarged heads 8, 9 which lie beneath a 25 mica wall Ill the periphery of which engages an annular ledge II within the lower end of the shell to thereby prevent upward movement of said rods. The outer end of the rod 6 is riveted or flanged so as to connect it to a circular conducting terminal i2 of copper which rests upon a mica member I3 at the outer end of the casing 5, and the outer end of the rod 'I extends through a hole Il in the terminal I2 and is likewise secured to a similar circular terminal 'I 5; the mem- $5 bers I2 and I5 being insulated from one another by a disc I6 of mica or equivalent material. The periphery .of the terminal I 2 is slightly conical, and the terminal I5 has an upwardly extending threaded post I1 to receive a nut I0. A conical 4e ring 20 surrounds the terminal I2 and has a supply conductor 2i connected to it, whereby a conducting path is provided leading to the rod I, and

a conductor 22 terminating in a plate 23 having a passage for the post l1 provides a conducting 45 path leading to the rod l. The ring 20 and plate 23 are spaced apart by an annular insulating member 2l from which it follows that tightening of the nut I9 acts to secure the conductors or leads 2|, 22 to the plug. The heads l, l provide go abutments which prevent upward movement of the rods t, I during the vfinal assembling of the plug when the outer ends of said rods are riveted or flanged over the terminal blocks I2, Il; and

the head 9 prevents the rod 1 from being pulledl u.

upward when the nut i9 is tightened to secure the supply leads 2i, 22 vto the plug terminals.

after the rods and the inner mica wall I have been a'sseinbledwith the shell;- but before .they outer insulating disc |,3 is put in place to 'close the upper end of the shell; alumina (A1203) being the preferred granular material used and the same being pressed, rammed or otherwise compacted within the space aforesaid provided for its reception. The particles of said material do not, however, adhere to one another throughout the mass thereof, so that the separate grains are free to move upon and relative to one another as the plug (including the granular insulation thereof) expands and contracts, due to heating, when the plug is in use. Said compacted granular material fills all minute interstices of the space which it occupies and establishes intimate contact with the rods 6, 1 and with the interior of the wall of the shell or casing 5 and, being a better conductor of heat than insulating materials heretofore .commonly used.4 it provides a relatively good path for the flow of heat from the rods to the shell and to the engine structure, and maintains the plug at a lower temperature than has heretofore commonly been the case in glow plugs.

In the form of my invention illustrated in Figure 1 a wire 26 which is of high electrical resistance extends from the upper end of the rod 6 (at which place it is welded or brazed to the rod) through the passage therein and to a point beyond the inner end of the plug, where it is coiled to form an igniting memberor part 21 when the plug is in use; and then through the passage in the rod 1 to the upper end thereof where it is likewise welded or brazed to said upper end as indicated at 28.

In the form of my invention shown in Figure 2 the metallic shell 29 is roughened upon its inner surface, as by a thread 30, to secure a more flrm bond between the granular material 3| and the casing; and an inwardly extending ledge 32 is provided at the inner end of the shell which supports a mica insulating member 33 through which the lower extremity of a single rod 34 extends, as shown.' This rod is shown as corrugated externally to provide a better bond between it and the granular packing material and increase the area of contact between the two, and secure a. better flow of heat from the rod to the granular material and to the shell or casing of the plug.

The upper end of the rod 34 extends beyond the outer end of the plug and is threaded to receive a nut (not shown) for fastening' a supply conductor to the plug; and an internally threaded.,

ring 35 is placed upon said upper end, the upper side thereof being in the same plane as the outer end of the shell 29 of the plug. A mica insulating member 36 rests upon the ring 35 and the outer end of the shell; and said insulating member 36 and the rod 34 are held in place (through the ring 35) by a gland nut 31 having an internally extending ledge which overlies said insulating member 36, as shown. Overlying said gland nut is a mica or equivalent washer 38 of insulating material; and a metallic nut 39 screwed upon the threaded outer end of the rod 34 serves to finish the assembling of the plug and form a seat for a supply conductor connector. The ring 35 prevents the rod 34 from being pulled upward as the nut 39 is tightened upon the terminal 34.

aiaeeev"adjacent =the inner .end of the plug. The other end of said wire, however, and'instead of return ing through a second rod as in Figure 1, enters a passage 43 provided in the shell 2S and is staked or welded therein, as indicated at 44; the return circuit being through the engine structure as in grounded ignition systems. 'I'he granular material 3| is the same in this second type of plug, and serves the same purpose and has the same features of advantage, as the granular material 25 present and hereinbefore referred to in describing the form of my invention illustrated in Figure 1; except that the threaded interior of the shell and the corrugated outer surface of the rod 34 form a path of greater area for the ow of heat to the shell than is present in said rst described form of my invention.

In the form of my invention illustrated in Figure 3 the shell or casing of the plug comprises a massive base part 45 threaded as shown to screw into a threaded opening in a cylinder wall; and

a. tubular part 46 the wall of which is made as thin as practicable tting within the base and welded or brazed thereto at 41, and which tubular part extends above the upper end oi' the base farther than the upper parts of the shells in Figures 1 and 2.

The purpose of this comparatively long and thin-walled shell part is to restrain the flow of heat along the upper part of the plug and to the current supply cables (not shown) more eii'ectively than is the case with the shorter and more massive upper end casings illustrated in Figures 1 and 2; the result being that the upper end of the plug and the cable terminals remain at a lower temperature inthis form of my invention than in the forms hereinbefore described.

In this Figure 3 form the inner end of the twopart casing is provided with an inwardly extending ledge 48 which supports a metal plate 49, which in turn supports a mica insulating member 50 against which the inner ends of metallic conducting rods 5I, 52 abut; these rods having passages at their inner ends within which short wire sections 53, 54 of a good heat conducting material are secured, as by welding at 55, 56. These wire sections extend through holes in the insulating member 50, and through larger holes (to avoid short circuiting the conducting rods) in the metallic plate 49; and the igniting member 51 of high resistance wire is butt welded to the extremities of the short wire sections as indicated at 58. 59.

The wire sections 53, 54 being of good heat conducting material, such as copper, but of small area in cross-section, it follows that they act to restrain the ow of heat from the igniting member 51 to the rods 5|, 52; and that such heat as flows to the rods is dissipated to their larger mass, with the result that the rods remain cooler than though such short wire sections were not present. Heat from the rods is dissipated through the granular insulating material of the plug and to the plug shell substantially as hereinbefore explained.

The space between the rods 5|, 52and the tubu- In the form of my invention illustrated in liig'-l ure 2 a high resistance wire 40 likewise extends lar part 46 of the casing is filled with a granular u nonconducting 'packing material Il. the same 'as in the forms oi my invention illustrated in Figures 1 and 2; and the outer ends of the rods extend through holes in a mica insulating member Il, and through larger holes in a metal plate n; which parts are shown as held in place by an inturnedledse Il at the outer end of the tubular shell part 4l.

The numerals Il and II designate the terminals of the plug to which supply conductors (not shown) are connected by any suitable connecting members; and a mica tube 66 .within the lower part o! the base ll surrounds the innerl ends of the rods Il.' I! to prevent them from being Short circuito!! by accidental Contact with theY base. The granular packing material il extends inward to thc insulating member 5l and fills the interstices between the inner ends oiA the rods and the mica tube as shown at 61.

l0.I Having .thus described and explained my inseparate and independent of one another and located one at the inner and the other at the outer end of said shell, and having holes through which the ends of said rods extend; and a mass of non-conducting granular material filling the space between said rods and said shell.

2. A glow plug comprising a hollow cylindrical shell or casing adapted to fit within an opening in the wall of an internal combustion engine cylinder; two metallic rods within said shell and extending longitudinally thereof, and the inner endsof which rods are provided with short sections of wire of good heat conducting material;

u an igniting member welded to the extremities` of said short wire sections, and which member is located adjacent the inner end of the plug; insulating members at the inner and outer ends of said shell and having holes through which the ends of said rods extend; and a mass of non-conducting granular material illling the space be-- tween said rods and said shell.

3. A glow plug comprising a hollow cylindrical shell or'casing adapted to t within an opening u in the wall of an internal combustion engine cylinder; two metallic rods within said shell and exf tending longitudinally thereof, and each of which has a passage extending throughout its length; a wire of high electrical resistance extending through said passages and an intermediate portion of which forms an igniting member located adjacent the inner end of the plug; insulating members at the inner and outer ends of said shell and having holes through which the ends of said a rods extend; and a mass of non-conducting granular material filling the space between said rods and said shell.

l4. A glow plug comprising a hollow cylindrical shell or casing adapted to ilt within' an opening in the wall of an internal combustion engine cylinder; two metallic rods within said shell and extending longitudinally thereof; two circular terminals arranged one above the other and to which the outer ends of said rods are connected; said terminals being insulated from one another;

aisance aninsulating'memberatthe upncrendolsaid shell and whereby said terminals are insulated from said shell. said member having holes through which the outer ends of said rods extend; a second insulating member at the inner end of said shell and having holes through which the inner ends of said rods extend; an igniting member to which current is supplied through said rods, and which member is located adjacent the inner end of the plug; and a mass of non-conducting granular material illling the space between said rods and said shell.

5. A glow plug comprising a hollow interiori! threaded cylindrical shell or casing adapted to fit within an opening in the wall of an internal combustion enginecylinder; a corrugated metallic rod within said shell and extending longitudinally thereof; an igniting member located adjacent the inner end of the plug; a circuit including said rod as a part thereof, and through which current is supplied to said igniting member; insulating members at the inner and outer endsof said shell and having holes through which the ends of said rod extend; and a mass of non-conducting granular material filling the space between said rod and said shell and forming an insulator for said rod.

6. A glow plug comprising a hollow cylindrical shell or casing adapted to it within an opening in the wall of an internal combustion engine, and which shell has an inwardly extending ledge at its inner end; an insulating member resting upon said ledge and having a hole therethrough; a metallic rod within said shell and extending longitudinally thereof and the inner end of which extends through the hole in said insulating mem# ber, and the outer end of which rod is threaded; an internally threaded ring in engagement with the thread upon said rod, and the upper surface of which lies in the plane of the upper end of said shell; a second insulating member resting upon the upper end of said shell and upon said ring, and which member has a hole extending therethrough through which the outer end of said rod extends; a gland nut in threaded engagement with the upper end of said shell and having an inwardly extending flange which engages the upper surface of said second insulating member to` thereby hold the plug parts in assembled relation; an igniting member located adjacent the ,inner end of the plug; a circuit including said rod as a part thereof, and through which current is supplied to said igniting member; and a mass of non-conducting granular material filling the space between said rod and said shell and forming an insulator for said rod.

7. A glowv plug comprising a hollow cylindrical shell or casing adapted to fit within an opening in the wall of an internal combustion engine cylinder; a metallic rod within said shell and extending longitudinally thereof, and which rod has a passage extending throughout its length; a wireof high electrical resistance extending through said pasasge and beyond the inner end of the plug to form an igniting member; a circuit includingsaid rod as a part thereof, and through which current is supplied to said igniting member; and insulating means for insulating said rod from said shell.

8. A glow plug comprising a hollow cylindrical shell or casing adapted to t within an opening in the wall of an internal combustion engine cylinder; a metallic rod within said shell and extending longitudinally thereof, and the inner end of which rod is provided with a short section oi' wire oi good heat conducting material; an igniting member welded to the extremity of said short wire section, and which member is located adiacent the inner end of the plug; a circuit including said rod and short wire section as parts thereof, and through which current is supplied to said igniting member; and insulating means for insulating said rod from said shell.

9. A glow plug comprising a hollow cylindrical shell or casing made up of a comparatively massive base part adapted to fit within an opening in the wall of an internal combustion engine cylinder, and a tubular part extending from said base part and having a comparatively thin wall to restrain the flow of heat to the outer end of the plug; a metallic rod within said shell and extending longitudinally thereof, and the inner end of which rod is provided with a short section of wire of good heat conducting material; an ignitlng member welded to the extremity of said short Wire section, and which member is located adjacent the inner end of the plug; a. circuit including said rod and short Wire section as parts thereof, and

through which current is supplied to said igniting member; and insulating means for insulating said rod from said shell.

10. A glow plug comprising a hollow cylindrical shell or casing made up of a comparatively massive base part adapted to iit within an opening in the wall of an internal combustion engine :gn-rases cylinder, and a tubular part extending from said base part and having a comparatively thin wail to restrain the iiow of heat to the outer end of the plug; two metallic rods within said shell and extending longitudinally thereof, and the inner ends of which rods are provided with short sections of wire of good heat conducting material; an igniting member welded to the extremities of said short wire sections, and which member is located adjacent the inner end of the plug; insulating members at the inner end of said base part and at the outer end of said tubular part and having holes through which the ends of said rods extend; and a mass of non-conducting granular material filling the space between said rods and vsaid shell.

11. A glow plug comprising a hollow'cylindrical shell or casing adapted to fit within an opening in the wall of an internal combustion engine cylinder; a metallic rod within said shell and extending longitudinally thereof; an igniting member located adjacent the inner end of the plug; a circuit including said rod as a part thereof, and through which current is supplied to said igniting member; insulating members at the inner and outer ends of said shell and having holes through which the ends of said rod extend; and a mass of granular alumina -lling the space between said rod and said shell and forming an insulator for said rod.

HECTOR RABEZZANA. 

